1. Field of the Invention
The present invention is related to key-actuated locking devices.
2. Description of the Prior Art
Key-actuated locks having a conventional tumbler and spring mechanism that establishes an electrical contact which either electrically opens the lock or sets off an alarm are generally well-known in the prior art. These types of locking devices are described in considerable detail in the following patents.
______________________________________ Golokow et al. U.S. Pat. No. 2,057,301 Aid 2,905,926 Katz 3,408,838 Kramasz et at. 3,415,087 Erez 3,596,014 Katz 3,608,342 Wood et al. 3,764,859 Schlage 3,801,755 Sasaki 4,023,161 Lipschutz 4,025,740 Lumme 4,029,919 Sung 4,146,761 Chan 4,157,479 ______________________________________
The Golokow et al. U.S. Pat. No. 2,057,301 describes a lock that completes an alarm circuit when an improper key is placed in the lock. The forward serrated edge of the improper key pushes the last tumbler of the lock which completes the alarm circuit. The proper key has a forward cut-out that avoids pushing up the last tumbler and avoids completing the alarm circuit. The Lumme U.S. Pat. No. 4,029,919 also achieves this feature with angular movement of the inner cylinder of a rotatable lock.
The Aid U.S. Pat. No. 2,905,926 describes a key-actuated device that has spring biased tumblers which act as switches for permitting access to the key holder while also identifying the key holder.
The Katz Pat. No. 3,408,838 describes tumblers in a key-actuated lock that have conductive rings. When the conductive rings are aligned, they complete a door unlocking circuit.
The Kramaz et al. U.S. Pat. No. 3,415, 087 describes a key-actuated lock that when rotated closes through its serrated edges predetermined switches which are connected to a logic circuit. The logic circuit determines whether access is permitted to the key holder.
The Erez U.S. Pat. No. 3,596,014 describes a "Yale-type" lock with tumblers having a conductive strip positioned on a side of the tumblers opposite the key. If an incorrect key is placed in the lock, the key through its improperly positioned serrated edges causes one of the tumblers to come in contact with the conductive strip, placing the lock in an alarm mode. A correct key does not allow the tumblers to contact the strip.
The Katz U.S. Pat. No. 3,608,342 describes a tumbler/spring operated door lock which electrically actuates, through conducting tumblers, an electrically actuated door latch.
The Wood et al. U.S. Pat. No. 3,764,859 describes a similar lock for an automobile. The tumblers have conductive surfaces and tumbler receptacles have conductive linings, together forming switches. When the proper switches are turned on, forming a proper code, an electrical circuit allows oil to flow to the transmission by way of a solenoid valve, enabling the automobile to run.
The Schlage U.S. Pat. No. 3,801,755 also describes a tumbler/spring actuated lock. The spring, upper tumblers, rotating inner cylinder and a conductor attached to one end of the spring complete a circuit that places the lock in an open mode when the tumblers are placed in alignment, thus allowing the inner cylinder to be moved angularly. The Saski U.S. Pat. No. 4,023,161 similarly describes a lock which has a key which when inserted closes the proper switches defining the proper code, permitting access to the user. The key is cylindrical and has a plurality of grooves of varying lengths which cooperate with push pins in the lock forming the switches. A binary code is established and identifies the key user.
The Lipschutz U.S. Pat. No. 4,025,740 describes a tumbler lock that accepts a cylindrical key having a driver of non-circular cross-sectional shape. The key, when turned in an angular direction, will ensure that at least one device essential for the operation of a motor vehicle is placed in an operational mode by way of a cooperating electrical circuit.
The Sung U.S. Pat. No. 4,146,761 describes a key-actuated electric lock having a distal end portion which activates an electric circuit after spring-biased tumblers are aligned and the inner cylinder is allowed to move angularly.
The Chan U.S. Pat. No. 4,157,479 describes a key having resistors that are connected to other resistors within a lock. When the key is inserted a bridge circuit is formed. A sensing branch of the bridge circuit is coupled to an anti-theft switch in a car, and in the event that current flows through the sensing branch, the anti-theft switch is opened preventing activation of the starter motor of the car.
Some of the above-mentioned patents use a switching mechanism which takes a considerable amount of space, either in the form of the traditional tumbler mechanism or a separate switch. Typically, the operable portion of a lock has a very limited amount of space limiting the size of the key needed to open the lock. A separate switch to electrically actuate the lock adds a considerable cost to the lock. All of the above-mentioned patents use switching mechanisms which have metal components that are subject to wear and corrosion over a long period of time. Mechanical tolerances become a significant problem with these types of switching mechanisms, since both the keys and the switching mechanism are subject to wear.
The Benford U.S. Pat. No. 3,500,326 describes a mechanically programmed encoder system. As a key with serrated edges is placed in the key passageway of the lock, the serrated edges pass a sensor within the lock. The sensor transmits signals in the form of a code to a programmed decoder system. The decoder system receives and analyses the code and allows access to the user. The transmitter may be either a pair of switches, photocells or any other type of device that can detect the serrated edges of the key as the edges pass by. In addition, the serrated edges may also be placed on the outer surface of a cylindrical key which when turned angularly passes the serrated edges past the sensor.